In the past, the development of effective treatments for feeding disorders in cattle, sheep and goats has been spurred by a desire to maximize yields of meat and dairy products. Existing drug-based treatments (see, e.g., U.S. Pat. No. 4,761,426 issued to Martin, et al., and U.S. Pat. No. 4,405,609 issued to Potter), however, have the serious drawback of rendering products from treated animals unsalable for long periods under laws designed to protect consumers from harmful drug residues. Farmers, unhappy with the need to choose between low yields or unsalable products, have long sought the development of alternative, drug-free dietary treatments. As farmers expand into other livestock markets, such as the raising of ostriches and emus for yields of meat and eggs, similar problems occur. The goals of drug-free dietary treatments are generally, improved growth and performance, and especially, appetite stimulation and reestablishment of the rumen or gastrointestinal microbial populations necessary for proper digestion.
Much attention has been given in recent years to the use of certain microorganisms as dietary adjuncts in efforts to improve the growth and performance of livestock in general, and reestablishment of rumen or gastrointestinal microbial populations in ruminant animals. Such dietary cultures are known as probiotics or direct-fed microbials. (Gilliland, S. E., 8th Int'l. Biotech. Syn. Proc., Vol. 2, pp. 923-933 (1988)). Generally, the microorganisms of such probiotics are those that are expected to grow and/or function in the intestinal tract or in the rumen of the particular animal and can exert certain metabolic actions that influence that animal. Various gastrointestinal tract microorganisms which have been considered for this type of usage include Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus casei, Lactobacillus lactis, Pediococcus cerevisiae and Streptococcus faecium. These bacteria perform one or more of the following functions: They compete for villi attachment sites with pathogenic microorganisms, control Ph(acidity) within the gastrointestinal tract, produce enzymes and other metabolites which benefit digestion, and produce substances capable of inhibiting the growth of other harmful microorganisms. Additional microorganisms that could be used for this purpose include the live cell yeast, Saccharomyces cerevisiae, the fungus, Aspergillus oryzae, and bacteria, Bifidobacterium longum and Propionibacterium freudenreichii or the taxonomic equivalents thereof. Live cell yeast cultures and fungi, such as Saccharomyces cerevisiae and Aspergillus oryzae, have been shown to produce beneficial enzymes and raise the pH in the rumen by enhancing the growth of bacteria that either utilize lactic acid or ferment feedstuffs to absorbable fatty acids. Bifidobacteria species have been shown to be a major colonizer of the undeveloped rumen of newborn cattle and the lower intestine of all newborn animals. Bifidobacterium longum may also aid in intestinal/rumen pH control and enzyme production. Certain strains of Propionibacterium freudenreichii utilize rumen nitrates as a food substrate and are, therefore, beneficial in reducing nitrate toxicity in animals exposed to excessive amounts of that chemical. This might occur where the cattle are exposed to excess nitrates in feeds, to fresh pastures grown during drought conditions and to nitrates in water.
As known in the art, the Food and Drug Administration, Center for Veterinary Medicine has published a list of microorganisms which they have reviewed and have found to present no safety concerns when used in direct-fed microbial products in the Official Publication of the Association of American Feed Control Officials, Inc. (AAFCO) (1993) at pp. 148-149, the disclosure of which is hereby incorporated by reference. Many commercial direct-fed microbials are especially important in their non-spore forms, i.e. vegetative forms. These vegetative forms may be in the dormant state. These microbials are approved for animal feeding and are available to the public from several suppliers.
Common feed additives (AAFCO p. 248-253, 21 CFR .sctn.573 and 21 CFR .sctn.584) are known in the art as carriers for animal or livestock feeding purposes. Those which have been found to be safe when used in feed, are on the FDA's Generally Recognized as Safe (GRAS) lists. 21 CFR 584. The ingredient additives not defined by AAFCO appear on the "Least Common Federal Ingredients" list, (AAFCO p. 248-253).
To derive maximum benefit from use of probiotics, the microorganisms must survive and grow in the rumen and/or intestine. It is thus imperative that the probiotic contain viable and active microorganisms at the time of consumption. The microorganisms used as probiotics, therefore, must be stable during preparation and during storage prior to consumption.
The simplest approach to delivery of probiotics is to add cultures to animal feed. However, it appears that few direct-fed microbials are stable in feed for more than 3-5 days. (Aimutis, W. R., Feeds Management, Vol. 42, pp. 26-32 (1991)). Moreover, some feed contains antibiotics which are contrary to microbials stability. Yet other feed is pelleted, and most Lactobacillus species, which are predominant and beneficial intestinal species, are susceptible to the high temperatures, compression, aeration and mixing abrasion to which they are exposed during the pelleting process.
Another approach is to provide the bacteria themselves as a pellet or bolus. Many such bolus products are commercially available.
More recently, bolus or pellet formulations have been developed which include a combination of the microorganisms and dry vitamin and trace mineral supplements, as nearly simultaneous administration in vivo of these components has been suggested as being highly beneficial to achieving the goals of appetite stimulation and microbial population reestablishment. Many of these bolus formulations are available commercially. It has been found, however, that the supplements and microorganisms are incompatible as the vitamin and mineral levels commonly used and efficacious for livestock are toxic to the microorganisms in many formulations. The toxicity is dependent upon concentration of the vitamins and/or minerals and the microorganisms used. By "toxic" is meant that the vitamins and/or minerals inhibit, or prevent growth or diminish viability of the microorganisms. By viability is meant the capability of life. The toxicity is demonstrated in a reduction of shelf life of a microorganism. As the time period in which the microbials are in contact with the toxic substance increases, the concentration of the microbials (often expressed as colony forming units per gram i.e., CFU/g or colony forming units per bolus i.e., CFU/Bolus) as measured by standard testing procedures, decreases. This is also expressed as Percent Survival Rate of the microorganism observed over a period of time. As the time period increases, the Percent Survival Rate decreases.
Thus, the CFU's decrease as time increases. The population of viable microorganisms can be greatly reduced within a week or within approximately a month. As indicated previously, microorganisms are also sensitive to mixing abrasion, aeration, compression and high temperatures, all of which occur during conventional hard bolus production. Moreover, the bolus formulations also require binding, wetting and disintegrating agents, any or all of which may adversely affect the viability of the microorganisms. Such bolus products, therefore, have limited shelf stability or shelf life, in that, the population of viable microorganisms can be greatly reduced within about a week or about a month.
Thus, a persistent and vexatious problem, largely unattended by the prior art, is the lack of a method for simultaneously delivering incompatible substances in vivo to animals, when one of the substances is a viable microorganism culture.
Various prior art methods of physical separation, e.g., encoating, encapsulation and microencapsulation, of nutritional supplements are known, however, none adequately address the preparation and storage requirements of sensitive direct-fed microbial agents. For example, conventional microencapsulation subjects microorganisms to a number of potentially fatal packaging procedures and requires expensive materials, complex equipment, and carefully controlled environmental conditions. Polymeric microcapsules also require specific pH ranges or enzyme activities to effect release of their contents in vivo. These requirements often frustrate conventional laboratory assessment techniques and prevent effective nutrient release in animals whose rumen and/or gastrointestinal pH or enzyme balances have been disrupted by microbial depopulation.
U.S. Pat. No. 4,695,466 to Morishita discloses a multiple-encapsulation method. The Morishita process includes successively encapsulating oil solutions or suspensions in soft capsules. Although the method of Morishita has potential for delivery of two components in a single vehicle, the use of oil carriers presents insurmountable obstacles to the delivery of microorganisms and vitamin supplement components. It is unlikely that Morishita's soft outer capsules will be able to withstand common shipping, storage and administration conditions and also is unlikely applicable to commonly available microbial forms.
Despite recognition of the known drawbacks of prior art products, the art has not adequately responded to date with a method for delivery in vivo of the incompatible components, namely, direct-fed microbials and nutrient supplements nearly simultaneously to cattle, sheep, goats, and ratites.